Welcome Anjali to the forums!
If I add mulabandha a bit during "head to both knees" asana, at certain times I get a small sensation at the root that is enjoyable, but at the same time draining. Perhaps give it some time so that your body can re-adjust, as there might be a new dynamic coming into play, certainly one of greater energy, even if it does not feel that way for now.
Do keep us posted.